This invention pertains to a method of coupling aryl and heteroaryl mono chlorides and more particularly to the use of a catalyst mixture of an anhydrous nickel compound and a ligand in the presence of a reducing metal in a dipolar aprotic solvent. Also, this invention relates to novel catalyst compositions.
Reactions which form carbon-carbon bonds are few although they are extremely useful in organic synthesis. In the formation of these bonds involving aryl groups, coupling is usually accomplished through the use of a metal. The use of copper in the Ullman reaction is described in Chem. Rev. 38,139 (1946); 64, 613 (1964). The use of nickel complexes was described by M. F. Semmelhack, et al in J. Am. Chem. Soc., 93, 5908 (1971). The use of palladium complexes was described by F. R. S. Clark, et al, J. Chem. Soc. Perkin I, 121 (1975). The latter reactions with nickel or palladium complexes have the advantage of proceeding at moderate temperatures but are disadvantageous in that aryl chlorides were either completely unreactive or gave very poor yields.